Detection of virulence factors and antifungal susceptibility of human and avian Aspergillusflavus isolates

Abstract

Aspergillusflavus is the second leading cause of invasive and non-invasive aspergillosis. Secretion of hydrolytic enzymes is considered as a virulence factor in this species. Our work aimed to study in vitro production of some virulence factors, to evaluate the biofilm production against human and avian A. flavus isolates and to investigate the antifungal susceptibility agents. Hydrolytic enzymes, biofilm production and molecular typing were studied for 62 human and 36 avian A. flavus isolates by specific solid media and six microsatellite markers. The susceptibility to antifungal agents was evaluated for 37 human isolates. All human and avian A. flavus isolates showed positive activities of extracellular hydrolase: phospholipase, protease and hemolysin. A positive elastase activity was seen in 64.51% of human A. flavus isolates and 86.1% of avian A. flavus isolates. All A. flavus in these two populations formed biofilms. Statistical significant difference was observed for the mean phospholipase activities (P=0.025) and biofilm quantification (P=0.0001) between human and avian A. flavus isolates. The in vitro susceptibility results showed a resistance in 83.7%, 81.08% and 16.21% of A. flavus isolates respectively to amphotericin B, itraconazole and posaconazole. No association was noted between all virulence factors and the genotypes of human and avian isolates. Our study allowed us to show that human strains have a higher production of extracellular hydrolases and biofilm then avian strains. These virulence factors appear to act synergistically to contribute to the virulence of A. flavus strains. Moreover, significant correlation between virulence patterns and antifungal susceptibility profiles was observed.